Water soluble or water-dispersible films are known, but there are few commercially viable examples. Polyvinyl alcohol (PVOH) film constitutes nearly all of the volume and is used for disposable bags and packaging. A solution process is typically employed for PVOH since it lacks thermal stability. This is cumbersome and adds to the cost of the manufactured film.
Sulfopolyesters are another class of materials where cast films may subsequently be re-dispersed into water. Typical sulfopolyesters, such as those disclosed in U.S. Pat. No. 3,734,874, result in brittle films or films having low strength.
More recently, a family of branched sulfopolyesters has been developed for water-dispersible adhesive formulations as disclosed in U.S. Pat. Nos. 5,543,488; 5,552,495; 5,552,511; 5,571,876; and 5,605,764. These polymers are easily dispersible into water, but have glass transition (Tg) values not greater than 20.degree. C. and result in films that undergo blocking during storage.